In one variation of deep-bed filtration the liquid is passed upwards through a fluidized bed of particles. In this variation, filtration efficiency is very much dependent on some type of attraction between the bed particles and the suspended particles, otherwise the suspended particles flow easily through the much larger voids in the fluidized bed, and filtration efficiency is low. When this inter-particle attraction exists, another variation in filtration procedure is possible. This is to pass the fluidized bed downwards, by gravity, through the liquid to be filtered. This variation is the subject of this paper. The ability of falling particles to induce a flow pattern in the body of the liquid makes it possible to devise a very large scale continuous filtration operation, to clarify volumes too large for other filtration techniques, especially when the suspended solids are at a very low concentration. In all of the above, the word gas can be substituted for the word liquid, and the whole spectra of gas cleaning by falling liquid or solid particles opens up. One of these - the cleaning of dust from the atmosphere by falling raindrops - is a familiar and interesting example of simultaneous filtration and flow inducement.